Non-small cell lung carcinomas (NSCLC) represent approximately 80% of lung cancers, with a dismal 5-year survival rate of 15%.1 Tumor stage remains the strongest predictor of survival for these patients.2 Early-stage (I to II) patients are treated primarily by complete surgical resection. However, 30-55% of these patients develop recurrence and die of the disease,2, 3 implying that biological heterogeneity exists in patients and their tumors. Recent Phase 3 trials have established that adjuvant chemotherapy can significantly improve the survival of at least stage II-IIIA patients.4-8 Therefore, identification of additional markers that may accurately classify early stage NSCLC patients into significantly different prognostic groups would improve the selection algorithm for patients to receive adjuvant therapy. To date, neither tumor histological features nor the >50 potential cancer-associated proteins that have been investigated could serve as such a marker.9, 10 
Several NSCLC mRNA expression microarray studies have identified gene signatures that could subgroup patients into meaningful prognostic groups.11-16 However, these putative prognostic gene lists are characterized more by discordance than concordance (FIG. 1A). Cross-study analyses of the datasets using different statistical approaches or validation using quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) assays in an independent patient cohort have generated additional and different lists.17-19 Such discordances may be attributed to insufficiently-powered studies,20 and to variability in patient cohorts, expression profiling platforms or statistical methodologies. Further efforts to validate the prognostic value of these putative markers in large independent tumour/patient cohorts have been lacking.
There is a need to identify candidate markers to classify NSCLC patents into meaningful prognostic groups.